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      <title>NameServer功能与服务发现 - 交互式测验</title>
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    <body>
      <div class="main-wrapper">
          <div class="quiz-container">
            <div class="quiz-header">
              <h1>NameServer功能与服务发现 - 交互式测验</h1>
              <p>检验你对文档内容的理解程度</p>
            </div>
            <div id="quiz-content">
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      <script>
        const quizData = [
  {
    "question": "在 RocketMQ 架构中，NameServer 的核心职责是什么？",
    "options": [
      "负责持久化存储消息数据，确保消息不丢失。",
      "充当服务注册与发现中心，管理 Broker 的路由信息。",
      "协调分布式事务的提交与回滚。",
      "直接参与并计算消费者之间的负载均衡策略。"
    ],
    "correctAnswerIndex": 1,
    "explanation": "NameServer 的核心定位是服务注册与发现。Broker 启动后向 NameServer 注册其元数据（如地址、Topic信息），客户端（Producer/Consumer）则从 NameServer 查询这些路由信息，以确定与哪个 Broker 通信。它不存储消息（这是 Broker 的职责），也不直接执行负载均衡计算（这是客户端根据路由信息在本地执行的）。",
    "source": "文档中「NameServer的核心功能」部分",
    "hint": "文档开篇第一句就定义了 NameServer 的角色，它负责管理 Broker 的注册信息并提供什么服务？"
  },
  {
    "question": "文档中反复强调 NameServer 采用“无状态设计”，这一设计的关键特征是什么？",
    "options": [
      "NameServer 实例之间通过 Raft 协议选举 Leader 并同步路由数据。",
      "NameServer 将路由信息持久化到磁盘，以便在重启后快速恢复。",
      "NameServer 实例之间相互独立、无数据同步，路由信息仅存于内存中。",
      "NameServer 依赖像 ZooKeeper 这样的外部组件来维护集群状态。"
    ],
    "correctAnswerIndex": 2,
    "explanation": "NameServer 的“无状态”核心在于其各个实例的独立性。它们之间不通信，不进行数据同步。所有路由信息都存储在各自的内存中，并通过 Broker 的心跳机制动态构建和维护。这种设计极大地简化了部署和运维，并天然支持高可用。",
    "source": "文档中「3. 无状态设计」和「NameServer的高可用设计 -> 1. 无状态设计」部分",
    "hint": "思考“无状态”如何让 NameServer 实例之间可以做到“无中心化”和“无数据同步”。"
  },
  {
    "question": "NameServer 是如何判断一个 Broker 实例已经下线并将其从路由表中移除的？",
    "options": [
      "通过定期向所有 Broker 发送探测请求，若连续三次无响应则认为其下线。",
      "当客户端连接 Broker 失败时，会向 NameServer 报告，累计报告超过阈值后移除该 Broker。",
      "Broker 正常下线时会发送注销请求，但对于异常宕机，NameServer 无法感知。",
      "NameServer 会检查 Broker 的心跳时间戳，如果一个 Broker 超过120秒未发送心跳，则认为其不可用并移除。"
    ],
    "correctAnswerIndex": 3,
    "explanation": "NameServer 依赖于 Broker 的主动心跳来维持其存活状态。Broker 默认每30秒发送一次心跳。NameServer 内部有一个定时任务，每10秒扫描一次所有 Broker 的最后心跳时间，如果发现某个 Broker 的最后心跳时间距今已超过120秒，就会判定该 Broker 失效，并将其相关的路由信息全部移除。",
    "source": "文档中「4. 心跳机制」部分",
    "hint": "文档中提到了两个关键的时间数字：Broker 发送心跳的频率，以及 NameServer 判定超时的阈值。"
  },
  {
    "question": "根据文档，RocketMQ NameServer 集群是如何实现高可用的？",
    "options": [
      "通过部署多个无状态、相互独立的实例，客户端和 Broker 配置所有实例地址，实现故障时自动切换。",
      "通过主备（Master-Slave）模式，当主 NameServer 宕机后，备用 NameServer 会自动接管服务。",
      "通过共享存储（如 NFS 或数据库）来保证所有 NameServer 实例的数据一致性。",
      "通过在所有 NameServer 实例间运行 Paxos 协议来同步路由信息，确保数据强一致性。"
    ],
    "correctAnswerIndex": 0,
    "explanation": "NameServer 的高可用性建立在其无状态设计之上。通过部署多个对等的 NameServer 实例，并将所有实例的地址配置给 Broker 和客户端。当任何一个 NameServer 实例宕机时，Broker 仍然能向其他实例发送心跳，客户端也能从其他实例获取路由信息，从而实现了简单而高效的故障转移。",
    "source": "文档中「NameServer的高可用设计」部分",
    "hint": "高可用性的实现与 NameServer 的“无状态设计”和“多实例部署”密切相关。"
  },
  {
    "question": "一个正在运行的 RocketMQ 客户端（Producer 或 Consumer）通常会通过哪种机制来更新其本地缓存的路由信息？",
    "options": [
      "仅在启动时从 NameServer 获取一次，之后除非重启，否则不再更新。",
      "等待 NameServer 在路由信息发生变化时主动推送更新通知。",
      "定期（默认30秒）从 NameServer 拉取，并且在消息收发失败时也可能触发更新。",
      "只在消息收发失败时才会触发向 NameServer 的路由更新请求。"
    ],
    "correctAnswerIndex": 2,
    "explanation": "为了确保客户端的路由信息能及时反映集群状态的变化（如 Broker 上下线、Topic 扩容），客户端采取了“拉”模式。它会默认每30秒主动从 NameServer 拉取最新的路由信息。同时，作为一种快速失败恢复机制，当消息发送或拉取失败时，也会立即触发一次路由信息的更新。",
    "source": "文档中「3.3 客户端更新」部分",
    "hint": "客户端更新路由信息有两种主要时机：一种是定期的，另一种是异常触发的。"
  },
  {
    "question": "当一个 Broker 启动时，它会如何将其路由信息注册到 NameServer 集群？",
    "options": [
      "Broker 随机选择一个 NameServer 进行注册，该 NameServer 再将信息同步给其他实例。",
      "Broker 向其配置列表中的 **所有** NameServer 实例发送注册请求，并定期发送心跳。",
      "Broker 会向 NameServer 集群的 Leader 节点注册，由 Leader 负责分发信息。",
      "Broker 不会主动注册，而是等待 NameServer 通过广播发现并拉取其信息。"
    ],
    "correctAnswerIndex": 1,
    "explanation": "为了确保在任何一个 NameServer 实例上都能查询到路由信息，Broker 的行为是“广播式”的。它会读取配置中的 NameServer 地址列表，并向列表中的每一个 NameServer 都发送注册请求和后续的周期性心跳包。这与 NameServer 之间不通信的设计是相辅相成的。",
    "source": "文档中「1. Broker注册流程」部分",
    "hint": "考虑一下，既然 NameServer 之间不通信，Broker 必须怎么做才能让所有 NameServer 都知道它的存在？"
  },
  {
    "question": "如果一个客户端当前连接的 NameServer 实例突然宕机，根据文档描述的故障转移机制，会发生什么？",
    "options": [
      "整个消息收发服务会中断，直到该 NameServer 实例恢复。",
      "客户端在下一次请求（如获取路由信息）失败时，会从其本地配置的地址列表中尝试连接另一个可用的实例。",
      "其他 NameServer 实例会选举出一个新的“主”实例，并通知所有客户端进行切换。",
      "Broker 会检测到 NameServer 宕机，并主动推送新的可用 NameServer 地址给客户端。"
    ],
    "correctAnswerIndex": 1,
    "explanation": "客户端的故障转移机制是简单而有效的。每个客户端都持有一份完整的 NameServer 地址列表。当它尝试与当前的 NameServer 通信失败时（无论是连接失败还是请求超时），它会简单地从列表中选择下一个地址进行尝试，直到找到一个可用的 NameServer 实例。这个过程对业务是透明的。",
    "source": "文档中「3.1 客户端故障转移」部分",
    "hint": "客户端本身就持有所有 NameServer 的地址列表，当一个“向导”联系不上时，它会怎么做？"
  }
];
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            const totalQuestions = quizData.length;
            const answeredCount = userAnswers.filter(a => a !== null).length;
            const wrongCount = answeredCount - correctCount;
            const skippedCount = totalQuestions - answeredCount;
            const accuracy = totalQuestions > 0 ? Math.round((correctCount / totalQuestions) * 100) : 0;
            const errorRate = totalQuestions > 0 ? Math.round((wrongCount / totalQuestions) * 100) : 0;

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                '<div class="final-score-container">' +
                '<h2>答题报告</h2>' +
                '<div class="score-summary">' +
                '<div class="score-card">' +
                '<h3>得分</h3>' +
                '<p>' + correctCount + ' / ' + totalQuestions + '</p>' +
                '</div>' +
                '<div class="score-card">' +
                '<h3>正确率</h3>' +
                '<p>' + accuracy + '%</p>' +
                '</div>' +
                '<div class="score-card">' +
                '<h3>错误率</h3>' +
                '<p>' + errorRate + '%</p>' +
                '</div>' +
                '<div class="score-card score-details">' +
                '<table>' +
                '<tr><td>正确</td><td>' + correctCount + '</td></tr>' +
                '<tr><td>错误</td><td>' + wrongCount + '</td></tr>' +
                '<tr><td>未答</td><td>' + skippedCount + '</td></tr>' +
                '</table>' +
                '</div>' +
                '</div>' +
                '<div class="report-actions">' +
                '<button id="review-btn">回顾测验</button>' +
                '<button class="primary" onclick="location.reload()">再试一次</button>' +
                '</div>' +
                '</div>';

            let reportEl = document.querySelector('.final-score-container');
            if (reportEl) {
                reportEl.remove();
            }
            quizContentEl.insertAdjacentHTML('beforeend', finalScoreHtml);
            document.getElementById('review-btn').addEventListener('click', reviewQuiz);
        }

        function reviewQuiz() {
            const reportEl = document.querySelector('.final-score-container');
            if (reportEl) {
                reportEl.remove();
            }

            document.querySelector('.quiz-body').style.display = 'block';
            document.getElementById('quiz-footer').style.display = 'flex';
            
            currentQuestionIndex = 0;
            loadQuestion();
            updateNavigationButtons(); // Ensure nav buttons are correctly displayed
        }

        // Event Delegation for options
        optionsListEl.addEventListener('click', (event) => {
            if (event.target && event.target.matches('li.option-item')) {
                // Check if the question has already been answered
                if (userAnswers[currentQuestionIndex] === null) {
                    const selectedIndex = parseInt(event.target.dataset.index, 10);
                    selectOption(selectedIndex);
                }
            }
        });

        prevBtn.addEventListener('click', goToPreviousQuestion);
        nextBtn.addEventListener('click', goToNextQuestion);
        hintBtn.addEventListener('click', showHint);
        
        // 初始加载
        loadQuestion();
      </script>
    </body>
    </html>
  